1. Field of the Invention
The present disclosure relates to a liquid crystal display device (hereinafter, LCD) having an edge type backlight unit adopting a light emitting diode (hereinafter LED) as a light source. Especially, the present disclosure relates to an LCD adapting a guide panel having a reinforced structure.
2. Discussion of the Related Art
Nowadays, due to the characteristics of light weight, slim thickness, low consumption electric power, the liquid crystal display device (or, LCD) is widely applied more and more. The LCD is applied to the portable computer such as note book PC, the official automation devices, the audio/video devices and so on. The most used LCD shows the picture data by modulating the luminescence of the light incident from the backlight unit by controlling the electric field applied to the liquid crystal layer.
As the liquid crystal display device is not self-luminescent element, the liquid crystal display device requires a backlight unit for irradiating light to the liquid crystal display panel. There are two kinds of the backlight unit for LCD, one is the direct type backlight unit and the other is the edge type backlight system. For the edge type backlight unit, light source is equipped at the circumferences of the transparent light guide plate. The light is radiated from the light source to the side surface of the light guide panel, and is refracted and/or reflected to the front side on which the LCD panel is disposed. On the other hands, for the direct type backlight unit, a plurality of light sources are disposed under the back side of the LCD panel so that the light is directly radiated from the light source to the overall surface of the LCD panel.
Recently, for the light source of the backlight unit, a light emitting diode (or, LED) is mainly used. Especially, mostly used is the edge type backlight unit in which one side of the light guide disposed under the flat display panel such as liquid crystal display panel.
FIG. 1 is a perspective view illustrating a structure of the liquid crystal display panel according to the related art. Referring to FIG. 1, the liquid crystal display device comprises a liquid crystal display panel 12, and an edge type backlight unit disposed under the liquid crystal display panel 12.
The liquid crystal display panel 12 comprises an upper substrate, a lower substrate, and liquid crystal cells between the upper and lower substrates. The upper substrate of the liquid crystal display panel comprises color filters (not shown), black matrixes (not shown) and so on. The lower substrate of the liquid crystal display panel comprises signal lines such as data lines and gate lines crossing each other, and thin film transistors (TFTs) at the crossing corner of the signal lines. Responding to the scan signal through the gate line, the TFT supplies the data signal from the data line to the liquid crystal cells. At the pixel area defined by the data line and gate line, a pixel electrode is formed. Furthermore, a common electrode facing with the pixel electrode is also formed in the pixel area. For the vertical electric field type liquid crystal display panel such as a TN (Twisted Nematic) mode or a VA (Vertical Alignment) mode, the common electrode is formed at the upper substrate 104. Contrary, for the horizontal electric field type liquid crystal display panel such as IPS (In Plane Switching) mode or a FFS (Fringe Field Switching) mode, the common electrode is formed at the lower substrate 102 with the pixel electrode.
The edge type backlight unit includes a light source 15, a light guide plate 16, and a plurality of optical sheets 14. The light radiated from the light source 15 is diffused in the light guide plate 16 and refracted to the upper surface of the light guide plate 16 where the liquid crystal display panel 12 is located. Through the optical sheets 14, the light from the light guide plate 16 is evenly dispersed all over the surface of the liquid crystal display panel 12. The light source 15 is disposed at least one side of the light guide plate 16 to irradiate the light to the side surface of the light guide plate 16. The light guide plate 16 changes the light path incident from the side surface to the substantially perpendicular direction, i.e, to the upper side of the light guide plate 16. The optical sheets 14 comprise one or more prism sheets and one or more diffusion sheet. The optical sheets 14 can further include a dual brightness enhancement film (DBEF) for enhancing the brightness of the backlight.
A cover bottom 17 is disposed with housing the light source 15 and light guide plate 16 from bottom side. The cover bottom 17 is made of a material having high thermal conductivity for radiating the heat from the light source 15 to outside of the cover bottom 17 easily and high strength for preventing the elements therein. For example, the cover bottom 17 can be made of Aluminum (Al), Aluminum Nitride (AlN), Electrolytic Galvanized Iron (EGI), Stainless Steel (SUS), Aluminum-Zinc Alloy Coated steel sheet (i.e, Galvalume), Aluminum coated steel sheet (i.e, ALCOSTA), or Tin coated plate (i.e, SPTE (Steel Plate Tin Electric), SPTH (Steel Plate Tin Hot-dip) or SPTFS (Steel Plate Tin Free Steel)). Furthermore, ultra high thermal conductive materials can be coated on the surface of the plate for the cover bottom 17.
A guide panel 13 and a top case 11 are assembled with surrounding the circumferences of the liquid crystal display panel 12. As a molded frame made of the fiber glass reinforced plastic, the guide panel 13 wraps the circumferences of the upper surface and the 4 sides of the liquid crystal display panel 12 and the side surfaces of the backlight unit. The guide panel 13 supports the liquid crystal display panel 12, and evenly maintains the gap between the liquid crystal display panel 12 and the optical sheets 14. The top case 11 made of coated metal plate such as Electrolytic Galvanized Iron (EGI) covers the upper and side surfaces of the guide panel 13. The top case 11 is fixed at the goude panel 13 or the bottom cover 17 with hooks or screws.
In the liquid crystal display device, it is important to have strength enough to protect most of all elements including LCD panel and other parts from external vibrations and impacts. Especially, required is the backlight unit having a structure or means for protecting the liquid crystal display panel from vibrations or external impacts, as the liquid crystal display panel is getting thinner.